Tension control system



y 1950 E. FRISCH ETAL 2,508,153

TENSION CONTROL SYSTEM Filed July 17, 1947 2 Sheets-Sheet 1 WITNESSES: 5(9 95 INVENTORS May 16, 1950 E. FRISCH ETAL msxon comer. svsm 2 Sheets-Sheet 2 Filed July 1'7, 1947 INVENTORS WlTNESSES:

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Patented May 16, 1950 TENSION CONTROL SYSTEM Erling Frisch and William 0. Osbon, Pittsburgh, Pa., assignorsr to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application July 17, 1947, Serial No. 761,706

14 Claims. 1

Our invention relates, generally, to tension control systems, and it has reference, in particular, to control systems for regulating or controlling the operation of reel motors and the like, such as are commonly used with strip rolling mills of various types to maintain strip tension.

Generally stated, it is an object of our invention to provide a tension control system which is simple and inexpensive to manufacture, and which is reliable and eflective in operation.

More specifically, it is an object of our invention to provide for using a tension device for controlling the operation of a reel motor in a winding or unwinding reel system.

It is an important object of our invention to provide in a tension control system for using a regulating generator controlled by a tension device responsive to the position of the strip for controlling the operation of a reel motor to regulate the tension of the strip.

Another object of our invention is to provide, in a system of the character described, for using, in conjunction with the tension device, a regulating generator of the self-energizing type for normally controlling the operation of a reel motor to maintain a predetermined strip tension, and for changing the operating characteristics of the regulating generator so as to convert it to a generator of the ordinary type should the tension device operate to a predetermined minimum value position.

Yet another object of our invention is to provide for compensating for a change in coil diameter during a reeling operation, by utilizing a regulating generator for-controlling theoperation of a reel motor, and for using the output of the regulating generator for changing the field strength of the reel motor in accordance with the change in the coil diameter.

A further object of our invention is to provide, in a tension control system of the character de scribed, for maintaining the tension of a strip of material independently of the reel speed or the coil diameter.

In it also an important object of our invention to provide for maintaining a predetermined value of strip tension during a winding operation, and for maintaining a lower value of strip tension when the mill is stopped before the completion of a winding operation.

Other objects will, in part, be obvious, and will, in part, be described hereinafter.

In practicing our invention in one of its forms, a tension device is used to apply a lateral force to a strip of material for maintaining a substantially constant tension therein between a roll stand and a winding reel. The armature of the reel motor is energized from a common mill bus, and a booster generator is utilized to vary the voltage applied to the armature. The output voltage of the booster generator is controlled by a regulating generator having a control field winding connected in a bridge circuit, the balance of which is controlled by the tension device, in response to deviations from a normal operating position of the strip of material at the tension device. The energization of the motor field winding is controlled by a rheostat driven by a motor energized in accordance with the output voltage of the regulating generator. Auxiliary contacts on the mill master switch operate a transfer valve to reduce the fluid pressure supplied to the tension device when the mill is shut down before the completion of a winding operation. A limit switch responsive to the maximum deviation position of the tension device changes the regulating generator to a generator of the ordinary type when the strip breaks, or the tension is removed for any other reasons, so that the reel motor will not speed up unduly in an attempt to restore the strip to the predetermined operating position for which the tension device may be adjusted.

For a more complete understanding of the nature and scope of our invention, reference may be made to the following detailed description which may be studied in connection with the accompanying drawings, in which:

Figure 1 is a diagrammatic view of a reel control system embodying our invention in one of its forms; and

Fig. 2 is a diagrammatic view of a reel control system embodying our invention in a different form.

Referring to Fig. 1, the reference numeral It may denote, generally, a tension control system, wherein a reel motor l2, having an armature l3 and a field winding I4, is connected in driving relation with a reel l6 for winding a strip material I II which may be delivered thereto by a roll stand 20 of a strip mill, or the like. The roll stand may be representative of the first or last stand of a tandem mill, or the only stand of a single stand mill.

The roll stand 20 may be driven by a roll or mill motor 22 having an armature 23 and a field winding 24. The armature 23 may be supplied with electrical energy from a main mill bus comprising conductors 2G and 21, which may be connected to a main generator 28 having an armature 29 and a field winding 30.

The field winding 30 of the main generator may be energized from a suitable source of electrical energy, 'being, for example, connected to control bus conductors 32 through a master rheostat 33 having a limit switch 34 associated therewith which returns to the closed position whenever the rheostat is operated to the minimum or oiI" position.

The field winding 24 of the mill motor may be energized from the control bus conductors 32 through a field rheostat 36.

A booster generator 38 having a field winding 38, which may be energized from any suitable source of control voltage, may be provided for regulating the voltage applied to the armature 23 of the mill motor.

The armature ll of the reel motor l2 may also be energized from the main bus conductors 2G and 21, being connected therebetween in circuit relation with a booster generator 40 comprising an armature 4| with main and regulating field windings 42 and 43, respectively. The main field winding 42 may be connected across the main bus conductors 26 and 21 in circuit relation with a field rheostat 45, which may be operatively connected to the rheostat 36 of the mill motor. The regulating field winding 43 may be energized from a regulating generator 41 having an armature 48, a control field winding 49, and a selfenergizing field winding 50 of the series type which is disposed to supply the magnetomotive air gap losses of the regulating generator and maintain the output voltage thereof at any value which may exist under balanced operating conditions.

In order to provide for maintaining the tension. of the strip i8 a't-a predetermined value, a te sion device, designated. generally by the meral 52, maybe provided for subjecting the str J to a transverse deflecting force and for contrc1- ling the energization of the control field winding 49 of the regulating generator. As will be tie scribed more in detail hereinafter the tension device 52 has a normal operating position. range and the movements thereof are utilized so control the operation of the reel motor 53 as pull on the strip and maintain the tension regs. latin means within its operating range.

In order to elIect this result, the control field winding 45 may be connected across a bridge 0" cuit 54 including a pair of fixed resistors 55 a 56, and a pair of variable resistance elements 58 and 59. The bridge circuit may be energized. from the control bus conductors 32, and controlled or selectively varied in accordance with the position or movement of the movable portion 60 oi! the tension regulating means so as to reverswbly energize the field winding 49 depending on whether the tension of the strip I8 is above or below the desired value.

The movable portion 60 of the tension device 52 may comprise a tension roll SI for engaging the lower side of the strip l8, being, for example, mounted on a bell crank arm 62 which may be actuated by a fluid pressure device 64. Regulating means 63 may be provided for controlling the resistance of the elements 58 and 59, including a depending arm 65 on the bell crank 62 for progresslvely actuating one or the other of a plurality of flexible contact members 61 or 68 connected to the elements 58 and 59 to progressively shunt or remove the shunt from one or more steps of the variable resistance elements. The arm ll and contact members 61 and 88 may be so arranged that when the tension roll Cl is in the proper operating position for the desired strip tension the nearer oi the contact members H and 68 are in engagement. A dashpot 6! may be connected to the lever 82.

In order to provide for maintaining a predetermined value of tension in the strip I! under normal operating conditions, and for maintaining a reduced value of tension under stalled conditions, a transfer valve 10 may be utilized for connecting the fluid pressure device '4 to a source of fluid pressure represented by the conduit 1| through either a relatively high-pressure regulating device I2 or a relatively lowpressure regulating device 13. The transfer valve 10 may be provided with an operating winding 14 which may be connected to the control bus conductors 32 through the limit switch 34 to operate the valve to,connect the fluid pressure device 64 through the low-pressure regulating device 13 whenever the rheostat 33 is returned to the zero or 011" position to stop the mill.

In order to prevent the regulating generator 41 from attempting to speed up the reel motor I2 to maintain the predetermined value of tension in response to operation of the tension device 52 to its maximum deflection position whenever the strip breaks, or whenever the tension of the strip is substantially zero, as for example, during a threading operation, control means, such as the relay 16 may be provided. The relay [6 may have an operating winding 18 which may be connected to the control conductors 32 through a limit switch which is actuated to the closed position. when the bell crank arm 62 moves to the maximum deflection position.

The relay IE may be'arranged to shunt the self-energizing field. winding 50 of the regulating generator 4? and to transfer the control winding 49 thereof from the bridge circuit 54 and connect it to the constant voltage control conductors 32 through a rheostat 82, which may be used to adjust the free running speed of the reel motor to a value, such as may be used for a threading operation, and, which will be only slightly higher than the normal running speed. The regulating generator 4'! is thereby changed to a generator of the normal separately excited type.

For the purpose of minimizing the amount of correction which will be necessary for the booster generator All to provide during a winding operation, control means, designated, generally, b the numeral 84, may be provided for progressively increasing the energization of the field winding l4 of the reel motor as the diameter of the coil on the reel I6 increases during the winding operation.

The field winding I4 may be, for example, connected across the control conductors 32 in series circuit relation with a rheostat 86 having an operating motor 81 comprising an armature l8 and a field winding 89. The field winding 89 may be connected to the control conductors 32.

A control generator 90, having an armature 9|, a regulating field winding 92 and an auxiliary field winding 93, may be provided for normally efiecting the energization of the armature ll. The auxiliary field winding 93 may be connected across the armature 9| to provide a portion of the ampere turns required for operating the rheostat, but not suflicient ampere turns to operate it when the field winding 92 is deenergized. The regulating field winding 92 may be connected was sets the armature 48 oftheregulatinggencrator sion iii-the strip rags; willcontinueto occur dar ing a- ;winding operationas the diameter oi the coil increases.

Control means comprising push button switches 95 and may be provided for controlling the running and reset relays 91 and 98 which may be arranged to connect the armature 88 of the rheostat motor, either to the control generator 90 or to the control conductors 32. A rectifier 99 may be connected in circuit relation with the control generator 90 to prevent reverse operation of the rheostat motor 81, should the voltage oi. the regulating generator 41 be reversed at the start of a winding operation. Limit switches I and IM prevent overtravel oi the rheostat 86.

During operation, the tension means t'Lmaintains a substantially constant tension in the strip I8 over a relatively wide range of deflections from a normal operating position. As the roll 6| moves from the normal position, the arm 65 operates: to vary the resistance of the variable resistors 58 and 59 in opposite senses, depending on whether the strip I8 is deflected above or below the predetermined normal position. Accordingly, the energization of the control winding 49 of the regulating generator 41 will be so varied that the,booster generator Ill either increases or decreases the voltage applied to the armature I3 of the reel motor in order to restore thestrip I8 and the tension device 52 to the normal operating position.

As the diameter of the coil increases, the reel motor slows down, its armature current increases, and the tension in the strip increases, or tends to increase, so that the deflection oi the strip is reduced to below the normal value. Any movement of. the strip I-8 actuates the tension roll GI downwardly from the normal position, so as to progressively shunt a greater number of sections of the resistor 58, and a lesser number of the sections of the resistor 59.

Accordingly, the bridge circuit becomes unbalanced and a voltage appears across the control field winding 49 of the regulating generator 41. This voltage has a polarity such that the regulating generator 41 is caused to produce a voltage for energizing the regulating field winding 43 of the booster generator 48 in such a direction as to reduce the voltage applied to the armature I8 of the reel motor. This reduces thearmature current of the reel motor and the torque developed by the motor. Accordingly, the deflection of the strip I8 is increased, restoring the tension roll SI toward its previous or normal operating position.

When a voltage appears across the armature 48 of the) regulating generator 41 in response to operatloni'of the tension device 52, the field winding 82 of the control generator 98 is energized thereby, and the rheostat motor 31 is operated to increase the energizatlon of the field winding II, so that the reel motor may operate at th reduced speed and still provide the increased torque necessaryfto maintain the predetermined deflection in the strip I-8 without requiring an increase in the value of the reel motor armature current. This increase in field energization increases the counter electromotive force of the armature, and increases the deflection of the strip to the predetermined value, so that the tension device 52 operates to reduce the energlzation of the control field winding to zero, whereupon the rheostat motor II! The rheostat motor continues this intermittent operation and follows the reel,build-' the-operating range.

' lating generator through contact member 180.

At the same time, the control field winding 49 of the regulating generator is disconnected from the bridge circuit 54 by the opening of contact member 1617, and is connected in circuit relation with the control conductors 32 through the threading sl geed adjusting rheostat 82 by contact member Accordingly, the regulating generator 41 is changed from a regulating generator of the selfenergizing type, to an ordinary control generator of the separately-excited type. The generator 41 is thereby prevented from building up its voltage in an attempt to speed up the reel motor I2 to restore the predetermined value oi strip defiection. Instead, the generator 41 merely generates suificient voltage, as determined by the operating position of the rheostat 82,.so as to operate the reel motor at substantially threading speed which may be slightly in excess of the normal running speed. The field winding 92 of the control generator 90 is disconnected from the regulating generator 41 by the opening of contact member 16d so as to prevent false operation of the field rheostat 86 when the diameter of the coil is not building up.

When the mill is brought to a stalled condition by returning the rheostat 33 to its "of!" position to reduce the voltage of the main generator 28,

the strip tension may be maintained at a relatively low value since the switch 34 operates and energizes the operating winding 14 of the transfer valve 10. The transfer valve thereupon operates to connect the fluid pressure device 64 to the source of fluid pressure through the relatively low-pressure regulator 13 instead of through the relatively high-pressure regulator 12. The tension device 52 thereupon produces a lower value of tension.

.Reierring to Fig. 2, the reference numeral I02 may denote, generally, a reel control system, wherein the reel motor I2 having a driving connection with the reel It for winding a strip material I8, may be connected to the main bus conductors 26 and 21 of the mill in series circuit relation with the booster generator 40 as described in connection with the control system shown in Fig. 1. In this instance, however, the regulating generator II for energizing the field winding 43 of the booster generator 40 is provided with a plurality of control field windings I05, I86 and II", instead of a single control field winding as 55 in the system of Fig. 1.

The field winding I05 may be energized from a pair of pilot generators II! and I II which may be operatively connected to the mill motor 22 and the reel motor I2, respectively. These pilot gen- ?0 erators may be connected in a series loop circuit with the control field winding I and a rectifier III. The rectifier functions to permit current to fiow only when the voltage of the pilot generator I I I associated with the reel motor is higher than that of theother pilot generator III. The field up ,nntil the-limit teases-em t, t t of:

Shouldthestrip' break or shouldthe'denection j of the tension roll 55 be increased'-'beyond a'-=predetermined maximum value for any-reason, the I windings I06 and I! or the regulating generator may be connected in opposition in circuit relation with the control conductors 02 and the variable resistance means 58 and 50, respectively, of the tension regulating means 52. Accordingly, they will neutralize each other when the arm I oi! the tension device 52 is in the middle or preferred position.

A field rheostat H4 may be provided in circuit with the field winding iii of the reel motor pilot generator III for adjusting the ampere turns of the control field winding I05 so as to completely neutralize the effect of the control field windings I08 and I0! when the tension is at a minimum value and the reel motor threading speed is slightly higher than the corresponding reel winding speed.

Under these conditions, the regulating generator I04 will function as a speed regulator when the tension roll is in the maximum deflection position during threading operations and will maintain the reel motor at substantially the threading speed. As soon as the reel is threaded, the reel motor speed will be reduced and the voltage of the pilot generator III is reduced. The rectifier H2 blocks reverse current flow, so that the current in the speed regulating field winding I05 will be reduced to zero. Since the tension device 52 is now operative to vary the energization of the control field windings I06 and I0! in opposite senses in response to variations in the tension roll position, these field windings are thereupon controlling in determining the output of the regulating generator. As a result, the regulating generator I04 is automatically transformed into a tension regulator throughout the winding operation. The limit switch and control relay used for the transfer, under these conditions, in the system shown in Fig. 1 may therefore be omitted while retaining all the operating benefits thereof. The system operates otherwise in the same manner as the system of Fig. 1.

From the above description and the accompanying drawings, it will be apparent that we have provided, in a simple and effective manner, for controlling the operation of a reel motor by using a regulating generator responsive to the operating position of a tension device. Apparatus embodying our invention is simple and inexpensive to manufacture and is reliable and effective in operation. While the invention has been described as applied to a winding reel, it is apparent that it may be readily adapted to an unwinding reel merely by reversing the connections to the armature 88 of the reel motor field rheostat motor 81 and reversing the connections of the reel motorarmature l3 and its associated booster generator armature 4| to the main mill bus conductors 26 and 21.

Since certain changes may be made in the above-described construction, and different embodiments of the invention may be made without departing from the spirit and scope thereof, it is intended that all the matter contained in the above description and shown in the accompanying drawings shall be considered as illustrative, and not in a limiting sense.

We claim as our invention:

1. In a control system for a reel motor having an armature and a field winding, circuit means connected to effect variable energization of the reel motor armature, control means responsive to the tension of a strip of material wound on the reel, regulating means controlled by the control means operable to vary the voltage applied to the reel motor armature from the circuit means, and additional circuit means responsive to the diameter of the coil on the reel connected to control energization of the reel motor field winding.

2. In a control system for a motor having a field winding and an armature connected in driving relation with a reel for strip material, circuit means controlling the energization of the armature including a regulating generator of the selfenergizing type, a tension device actuable to difierent operating positions by the strip material and operable to vary the output of the regulating generator, and control means operable to effect variable energization of the motor field winding in accordance with the diameter or the coil on the reel.

3. A control system for a reel motor having a field winding and an armature having a driving connection with a reel for a strip material comprising, circuit means including a booster generator connected in circuit relation with the armature to apply a variable voltage thereto, a regulating generator connected to control the output voltage of the booster generator, control means including a device responsive to the deflection of the strip from a normal position operable to vary the output of the regulating generator to maintain the strip in a predetermined operating position, and means including a rheostat energized in accordance with the output voltage of the regulating generator connected to efiect energization of the motor field winding.

4. A control system for a dynamo-electric machine having a field winding and an armature connected in driving relation with the reel for handling strip material, circuit means connected to effect energization of the armature including a regulating generator having a sell-energizing field winding and a control field winding, control means including means responsive to the position of the strip normally operable to effect energization of the control field winding to maintain the strip in a predetermined operating position, relay means operable in response to predetermined operation oi the tension means to render the self-energizing field winding ineffective and to render the tension means ineffective to energize the control field winding.

5. In a control system for a reel motor, a tension device responsive to the deflection from a predetermined position 01' a strip material wound on the reel, 9. regulating generator normally having predetermined operating characteristics operable in response to operation of the tension device to control the reel motor to maintain the strip in said predetermined position, and control means operable in response to operation of the tension device when the deflection of the strip from said position exceeds a predetermined amount to change the operating characteristics of the regulating generator.

6. A control system for a dynamo-electric machine having a driving connection with a reel for handling strip material comprising, a regulating generator having control field windings connected to effect energization of the dynamoelectric machine, circuit means including a tension device normally operable in response to the operating position of the strip to control the output voltage of the regulating generator to maintain the strip in a predetermined operating position, additional circuit means independent of the operating position of the strip, and control means responsive to deflection of the strip ten- 9 sion in excess of a predetermined maximum value operable to transfer control of the output voltage to the additional circuit means.

7. A control system for a reel motor having a driving connection with a reel arranged to handle strip material in connection with rolling means controlled by a master switch comprising, a regulating generatorconnected to effect energization of the reel motor, tension means normally operable to different operating positions to control the regulating generator and maintain a predetermined tension in the strip, and control means operable in response to operation of the master switch to stop the rolling means to vary the control of the tension means to maintain a lower tension.

8. A control system for a motor having a driving connection with a reel for strip material comprising, circuit means including a booster generator connected for supplying electrical energy to the reel motor, a regulating generator for controlling the booster generator, said regulating generator having a self-energizing field winding and a control field winding, control means normally connecting the control field winding for energization in accordance with the departure of the strip from a predetermined operating position, and relay means operable in response to predetermined departure of the strip from a predetermined operating position to render the self-energizing field winding ineffective and to transfer the control field winding to a source of substantially constant voltage.

9. In a control system for a reel motor having a driving connection with a reel handling strip material, circuit means controlling the reel motor including a regulating generator having a control field winding and a self-energizing series-type field winding normally effective to supply the air gap magnetomotive lossm of the generator, a tension device responsive to the deflection of the strip from a predetermined operating position, circuit means normally connecting the control field winding in a bridge circuit including control means responsive to the tension device to vary the balance of the bridge circuit, and switch means operable in response to operation of the tension device when the operating position of the strip departs more than a predetermined amount from the predetermined position to shunt the self-energizing field winding and transfer the control winding from the bridge circuit to a substantially constant voltage control circuit.

10. The combination with a mill motor having an armature connected in driving relation with a roll stand and energized from a power bus and a field winding energized from a- .control bus through a field rheostat, of a reel motor having a field winding and .an armature connected in driving relation with a reel for strip material passing through the roll stand, a booster generator having an armature connected in circuit relation with the motor armature and the power bus, said booster generator having main and regulating field windings, circuit means including a rheostat operatively connected to the mill motor rheostat connecting the main field winding to the control bus, a regulating generator having an armature and a self-energizing field winding connected in circuit relation with the regulating field winding, said regulating generator being provided with a control field winding, a bridge circuit having variable impedance means in adjacent legs thereof, circuit means connecting the control field winding in said bridge circuit, a tension device operable in response to variation of the strip material from a predetermined operating position to vary the impedances of the variable impedance means in opposite senses to control the reel motor to maintain the strip in said predetermined position, and switch means responsive to the operation of the tension device when the variation of the strip from the predetermined position reaches a predetermined maximum amount in one direction, said switch means being operable to shunt the self-energizing field winding of the regulating generator and transfer the connection of the control field winding thereof from the bridge circuit to the control bus.

11. In a control system for a reel motor having a field winding and an armature connected in driving relation with a reel handling strip material, control means including a regulating generator responsive to the operating position of the strip material connected to energize the armature of the reel motor, a motor-operated rheostat connected to efiect variable energization of the field winding of the reel motor, and a control generator responsive to the output of the regulating generator connected to energize the rheostat motor to vary the energization of the motor field winding in accordance with the diameter of a coil on the reel.

12. In a control system for a reel motor having a field winding and an armature connected in driving relation with a winding reel for strip material, control means including a regulating generator responsive to the operating position of the strip connected to control the operation of the reel motor to maintain a predetermined strip position, circuit means including a motor-operated field rheostat connecting the field winding of the reel motor to a source of electrical energy, said rheostat motor having a field winding energized from a source of control voltage and an armature, a control generator having a selfexcited field winding and a field winding energized from the regulating generator, and switch means selectively connecting the armature of the rheostat motor to the control generator during a winding operation and to the source of control voltage for resetting at the end of an operation.

13. In a control system for a reel motor having a field winding and an armature having a driving connection with a reel for strip material passing between the rolls of a mill stand, circuit means including a regulating generator connected to vary the energization of the reel motor armature, circuit means connected to control energization of the motor field winding in accordance with the output voltage of the regulating generator, control means responsive to a diflerence in speed between the mill stand and the reel motor normally operable tocontrol the output of the regulating generator, and tension means responsive to the operating position of the strip material for modifying the output of the regulating generator.

14. A control system for a winding reel used in conjunction with a mill stand comprising, a reel motor having an armature and a field winding, said armature having a drivingconnection 11 nected to eflect energization of the motor field winding in accordance with the output of the regulating generator, circuit means connecting one of said field windings for energization in accordance with a diilerential between voltages proportional to the speeds of the reel motor and the mili stand, and circuit means including a. tension device responsive to the operating position of the strip connected to efiect energization of a pair of said windings in opposite senses and to selectively vary the energization thereof in opposite senses, the energization of said pair 12 of winding: being balanced at a minimum value for the desired operating position.

ERLING FRISCH. WILLIAM O. OBBON.

REFERENCES CITED UNITED STATES PATENTS Name Date Edwards et al Dec. 22, 1942 Number 

